1. Field of the Invention
The present invention relates to a system for decrypting software which was distributed in encrypted state.
2. Description of the Prior Art
In recent years, with a spread of a CD-ROM drive, a distribution of the encrypted software using a CD-ROM as a medium is popular. This is derived from the fact that the CD-ROM medium can be manufactured at an extremely low cost and has a large capacity over 600 MB, and the CD-ROM drive becomes lower in price but higher in speed. Further, the CD-ROM is light and thin and can be therefore distributed while being inset in a magazine. This distribution mode is a novel mode that could not be seen in a distribution of the software using a floppy disk as a medium.
On the other hand, the software stored in this CD-ROM is digital data and therefore has a risk of being easily illegally copied and installed. The term "install" is to load the software into a disk device (hard disk, a silicon disk, etc.) of a personal computer system. Hence, it is required that there also be established a system capable of preventing such illegal copying and installing on the distribution of the software by use of the CD-ROM.
Proposed under such circumstances was a software distribution system for distributing the software by use of the CD-ROM while preventing the illegal copying and installing.
For example, as illustrated in FIG. 39, there has been utilized a software distribution system in which plural kinds of practical version encrypted software and trial version non-encrypted software corresponding thereto are recorded on a single piece of CD-ROM, and this CD-ROM is distributed.
According to this system, a user 100 at first purchases a CD-ROM which stores the above contents from a sales shop 101 (the sales price of the CD-ROM is set comparatively low). Then, the user 100 tries the trial version software stored in the CD-ROM. This trial version software is, however, in the majority of cases, restricted functions such as being incapable of file storage and printing, etc. If there is software that the user wants to get as a result of a trial use of the trial version software, the user installs practical version software corresponding thereto into a personal computer system of the user's own.
The practical version software has been, however, encrypted, and it is therefore required that a decrypting key for decrypting the ciphers is inputted when the practical version software is installed. For this purpose, the user gets a contact with a management center (hereinafter referred to simply as a "center") 102 to which a work of setting a right of use is entrusted from a software rightful claimant (person possessed of copyright or the right of use) through a telephone or the like and thus makes a request for purchasing the decrypting key for the software. The center 102, on confirming a payment of money necessary for purchasing the decrypting key, vends and offers it to the user 100. The user 100 is allowed to decrypt the practical version software by inputting the decrypting key and thus can complete the installation.
According to this system, however, the decrypting key can be, as a matter of fact, used again and again. It is therefore possible to matter-of-factly install the decrypting key into a plurality of personal computer systems. Further, in fact, the user 100 can tell the decrypting key purchased a third party having no right and let them decrypt and install the practical version software. Those are illegal using conducts beyond the range allowed by an approval contract for using the software when the decrypting key is vended. A fist problem inherent in a conventional software decrypting system is that those illegal uses can not be effectively prevented.
Also, if a decrypting key which is effective only once with some methods is developed, the illegal use given as the first problem could be prevented. On the other hand, however, the following problems will arise. That is, even the user 100 set the right of use of the software by regularly purchasing the decrypting key wants to reinstall if some of files constituting the software are broken down or if drive setting (mapping) of the disk device is changed. Further, when this regular user 100 newly purchases a personal computer system, the user desires to delete (uninstall) a certain set of software installed in the previous personal computer system and to reinstall it into the new personal computer system as the case may be. Such reinstalling is normally a conduct falling within the range of the right of use of the software. Then, for executing the above valid reinstalling, the regular user 100 has to set the decrypting key once again. However, since the decrypting key purchased at first has already been used, it follows that the user 100 requests the center 102 for a free-of-charge distribution of the decrypting key.
The center 102 can not, however, distinguish whether the decrypting key requested by the user 100 intends the reinstalling or an illegal use such as informing the third party of the decrypting key. For this reason, the center 102 can not take measures such as offering the decrypting key which is free of charge in response to the request for reinstalling but rejecting the request for the illegal use as in the case of providing the decrypting key to the third party or demanding a running royalty for the decrypting key. This is a second problem inherent in the conventional software decrypting system.